Gel materials

Abstract

Methods of making gel materials are disclosed including mixing a water soluble crosslinkable matrix polymer, a particulate polymer material which has been crosslinked to a gel content of at least 55% and an aqueous solvent, and crosslinking the matrix polymer to form a gel matrix of the matrix polymer in which the particles of particulate polymer material are dispersed, each of the crosslinked matrix polymer and the crosslinked particulate polymer material being capable of absorbing water. Gel materials are also disclosed including particles of a particulate polymer material capable of absorbing water and which is crosslinked so that it has a gel content of at least about 55% dispersed in a matrix of a polymer which has been crosslinked to reduce its solubility in water so that it swells rather than dissolves in water, the size of at least 60% by weight of the particles of particulate polymer material being less than about 100 μm.

What is claimed is:  
     
       1. A method of making a gel material which comprises mixing a water soluble crosslinkable matrix polymer, a particulate polymer material which has been crosslinked so that it has a gel content of at least about 55%, and an aqueous solvent to form a mixture, and crosslinking said matrix polymer so as to form a gel matrix of said matrix polymer in which the particles of said particulate polymer material are dispersed, each of said crosslinked matrix polymer and said crosslinked particulate polymer material being capable of absorbing water. 
     
     
       2. A method as claimed in  claim 1 , including drying said gel material after said crosslinking of said matrix polymer. 
     
     
       3. A method as claimed in  claim 1 , wherein said particulate polymer material is present in said mixture in an amount of at least about 0.5% by weight. 
     
     
       4. A method as claimed in  claim 1 , wherein said matrix polymer comprises polyethylene oxide. 
     
     
       5. A method as claimed in  claim 1 , wherein said particulate polymer material comprises an acrylic acid or an ester or a salt thereof. 
     
     
       6. A method as claimed in  claim 1 , wherein said particulate polymer material comprises a starch. 
     
     
       7. A method as claimed in  claim 1 , wherein the gel content of said particulate polymer material is at least about 75%. 
     
     
       8. A method as claimed in  claim 1 , wherein the size of at least about 60% by weight of the particles of said particulate polymer material is less than about 100 μm. 
     
     
       9. A method as claimed in  claim 8 , wherein the size of at least about 85% by weight of the particles of said particulate polymer material is less than about 100 μm. 
     
     
       10. A method as claimed in  claim 1 , wherein said matrix polymer is present in said mixture in an amount of at least about 2% by weight. 
     
     
       11. A method as claimed in  claim 1 , wherein the ratio by weight of said matrix polymer to said particulate polymer material is at least about 0.1. 
     
     
       12. A method as claimed in  claim 1 , wherein the ratio by weight of said matrix polymer to said particulate polymer material is not more than about 10. 
     
     
       13. A method as claimed in  claim 1 , wherein said crosslinking of said matrix polymer is initiated by means of ultraviolet radiation. 
     
     
       14. A gel material which comprises particles of a particulate polymer material which is capable of absorbing water and which is crosslinked so that it has a gel content of at least about 55% dispersed in a matrix of a polymer which has been crosslinked to reduce its solubility in water so that it swells rather than dissolves in water, the size of at least about 60% by weight of the particles of said particulate polymer material being less than about 100 μm. 
     
     
       15. A gel material as claimed in  claim 14 , wherein the gel content of said particulate polymer material is at least about 75%. 
     
     
       16. A gel material as claimed in  claim 14 , wherein said matrix polymer comprises polyethylene oxide. 
     
     
       17. A gel material as claimed in  claim 14 , wherein the ratio by weight of said matrix polymer to said particulate polymer is at least about 0.1. 
     
     
       18. A gel material as claimed in  claim 14 , wherein the ratio by weight of said matrix polymer to said particulate polymer material is not more than about 10. 
     
     
       19. A gel material as claimed in  claim 14  in the form of a sheet. 
     
     
       20. A gel material as claimed in  claim 14 , wherein said particulate polymer material comprises an acrylic acid or an ester or a salt thereof. 
     
     
       21. A gel material as claimed in  claim 14 , wherein said particulate polymer material comprises a starch.